Conventional liquid crystal displays include a reflective cavity, a light source, a display panel, and a diffuser. The light source is positioned such that it can inject light into the reflective cavity. The reflective cavity can take several general forms, such as a reflective surface forming one or more sides of an enclosure around the light source. Such reflective cavities can include a transparent light guide which is illuminated or edge lit along one or more edges. The display panel is spaced apart from the reflective cavity and may include a rear polarizer configured to allow passage of light having a plane of polarization that is substantially aligned with a predetermined polarization axis. The diffuser is typically disposed between the reflective cavity and the display panel and is configured to enhance the uniformity of light exiting the reflective cavity, including light that has a plane of polarization that is substantially aligned with the predetermined polarization axis.
Manufacturers typically incorporate liquid crystal display components that may be capable of optimizing energy usage, while having minimal weight, thickness, and cost. For example, manufacturers traditionally include diffusers formed of thin, highly transmissive materials having a surface texture on one or both sides to enhance light diffusion. The diffuser is typically placed such that an air gap is maintained between the diffuser and the other display components. The air gap enhances the diffusion properties of the diffuser and in addition reduces the likelihood of light absorption by non-ideal components in the vicinity of the diffuser. To further enhance energy efficiency, a pre-polarizing thin plastic film may be included that recycles unpassed light for subsequent passage through the diffuser or reflective cavity. The pre-polarizing film has conventionally been disposed between the diffuser and the display panel. In some display configurations, the pre-polarizing film specularly reflects light back to the diffuser and the reflective cavity which then return a portion of the light toward the display panel such that some of the reflected light becomes reoriented and allows passage of light that is substantially aligned with the polarization axis of the display panel. In other configurations, the pre-polarizing film backscatters the unpassed light but allows passage of light that is substantially aligned with the display panel polarization axis.
Although the above-described configurations have been adequate for smaller displays, they have exhibited drawbacks. In particular, as liquid crystal display sizes increase the structural integrity of certain sections of the film may become difficult to maintain. For example, the center of the film may become distorted or may inadvertently contact other display components when the display is shaken, dropped, or exposed to extreme thermal or humid environments.
One prior art method which can minimize film damage is lamination of a specular pre-polarizing film to a rear polarizer and applying the two to the display panel as a single sheet. However, it has been found that laminating the two polarizers together may undesirably alter some optical and physical characteristics of the liquid crystal display and may not be suitable for certain applications, such as avionics or military purposes. For example, the luminance, viewing angle, uniformity, or environmental performance of the liquid crystal display may not meet certain regulations that are set for displays used in avionics or military applications.
Accordingly, it is desirable to have a liquid crystal display that maintains structural and environmental integrity when produced in large sizes or used in demanding environments. In addition, it is desirable for the liquid crystal display to operate efficiently and to produce a high luminance that is suitable for use in avionics, military applications and commercial applications. Further, it is desirable for the liquid crystal display to have a wider illumination and viewing angle as compared to conventional displays. Moreover, it is desirable for the liquid crystal display to be relatively simple and inexpensive to manufacture. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.